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ELECTRIC MOTORS Motors convert electric energy to mechanical motion. The result is mechanical motion of the output shaft, that is a rotation about or a translation along the shaft, provided the load carried by the shaft does not exceed the maximum load the motor is designed to carry. Electrical current flowing in a loop of wire will produce a magnetic field across the loop. this loop is surrounded by the field of another magnet, the loop will turn, producing a force (called torque) that results
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    ELECTRIC MOTORS Motors convert electric energy to mechanical motion. The result is mechanical motion of the output shaft, that is a rotation about or atranslation along the shaft, provided the load carried by the shaft does not exceedthe maximum load the motor is designed to carry.Electrical current flowing in a loop of wire will produce a magnetic field across theloop. this loop is surrounded by the field of another magnet, the loop will turn,producing a force (called torque) that results in mechanical motion .The type of motor chosen for an application depends on the characteristics needed in thatapplication:These include:How fast you want the object to move,The weight, size of the object to be moved,The cost and size of the motor,The accuracy of position or speed control needed.The level of performance a motor can provide is described by its parameters . Theseinclude:Rated Speed : Speed measured in shaft revolutions per minute (RPM)Torque : Rotational force produced around a given point, due to a force applied at aradius from that point, measured in lb-ft (or, oz-in).HorsePower = Speed x Torque / 5252.11... :A measure of work expended: 1 HP = 33,000 foot-pounds per minute. Torque-Speed performance of a motor  The different types of motors possess different operating characteristics. ◦   Heavy Industrial applications: AC motors ◦   Mobile robotics & hobby robots: dc motor, dc servo motor, and steppermotors Types of motors:    AC motors    DC motors    DC servo motors    Stepper motors AC Motor Characteristics:    When power is applied, AC motors turn in one direction at a fixed speed.    Both reversable and non-reversable models available    Usually high voltage (110V AC and up)    Inexpensive and commonly available    Optimized to run at a fixed, usually high RPM.Types of AC motors :    (AC) induction motors    (AC) Single-phase motors    (AC) Synchronous motors 3-phase AC    Three or four wires that carry the same voltage at 3 equally-spaced phases: Single phase AC requires two wires (only 1/3 the current or power of 3-phase).  AC induction Motors    Induction motors  – simple, cheap, high-power, high torque, simplest are 3-phase.    Speed up to 7200 rpm: speed ~ 7200 / # “poles” of the motor.    Induction motors are brushless (no contacts between moving and fixed parts). Hireliability.    Efficiency high: 50-95 % Single-phase AC Motors:    Single-phase (induction) motors  – operate from normal AC current (one phase).Household appliances.    Single-phase motors use a variety of tricks to start, then transition to inductionmotor behavior.    Efficiency lower: 25-60%    Often very low starting torque. Synchronous AC Motors:    Designed to turn in synchronization with the AC frequency. E.g. turntablemotors.    Low to very high power.    If the applied load is greater than the capacity of the motor, the motor will stalland possibly burn out.      DC Motor Characteristics: DC power systems are not very common in the contemporary engineering practice. However,DC motors still have many practical applications, such automobile, aircraft, and portable electronics, in speed control applications…  An advantage of DC motors is that it is easy to control their speed in a wide diapason.DC generators are quite rare.Most DC machines are similar to AC machines: i.e. they have AC voltages and current withinthem. DC machines have DC outputs just because they have a mechanism converting ACvoltages to DC voltages at their terminals. This mechanism is called a commutator; therefore, DCmachines are also called commutating machines.    When power is applied, DC motors turn in one direction at a fixed speed.    They are optimized to run at a fixed, usually high RPM.    Torque is highest at the rated speed and lowest at low speeds.    Speed can be varied if a (pulse width modulation) PWM controller is added.    Almost all can be reversed.    Inexpensive and commonly available.    Available in wide range of speeds and power.    Suitable for turning, spinning, etc.    Not suitable for positioning unless some kind of position feedback is added.    If the applied load is greater than the capacity of the motor, the motor will stall andpossibly burn out.
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